Applicants claim priority under 35 U.S.C. xc2xa7119 of German Application Nos. 298 20 921.7 and 298 21 559.4, filed on Nov. 24, 1998 and Dec. 24, 1998, respectively. Applicants also claim priority under 35 U.S.C. xc2xa7120 of PCT/EP99/08902, filed on Nov. 22, 1999. The international application under PCT article 21(2) was not published in English.
The invention relates to a supercharger for a combustion engine of a motor vehicle, with a supercharger-driving input shaft that can be linked with a pulley drivable by the combustion engine via a switchable electromagnetic clutch, which has a frictional surface arranged on the front of the pulley, as well as a multi-plate carrier non-rotationally secured to the input shaft and a ring magnet or ring coil device accommodated in an annular slit in the pulley used to press a plate non-rotationally secured to the multi-plate carrier against the frictional surface.
The combustion engines in some passenger vehicles come standard with these superchargers. Correctly controlling the electromagnetic clutch here ensures that the supercharger only operates when the combustion engine is working at higher RPM""s and/or against a heavy load or strongly accelerated.
This makes it possible to ensure a good operating performance for the engine when driving slowly, in particular while driving in the city with a lot of stop-and-go action. In addition, the motor responds with a clearly stronger, instant acceleration when correspondingly depressing the accelerator pedal.
In addition, it is possible to have the combustion engine continuously drive the supercharger. In this case, it is standard for the air conveyed from the supercharger to first be routed to the inlet side of the engine only above an engine speed threshold, i.e., the engine works strictly as a naturally aspirated engine under this engine speed threshold. As a result, the stream of air generated by the supercharger at low engine speeds is prevented from having an undesired impact on the engine control electronics currently in use, since the sensors used to detect the aspirated stream of air can be affected, and the throttle valve in the aspiration system that is often nearly closed at low engine speeds can be undesirably moved by the stream of air from the supercharger.
The air stream generated by the supercharger is routed away via corresponding valves or air flap devices, through which the supercharger air stream can be released to the outside or relayed to the engine.
It is basically possible to retrofit motor vehicle engines with superchargers to increase the available power. However, superchargers for retrofitting are routinely not designed for combination with an electromagnetic clutch. Rather, it is assumed that the engine can continuously drive the supercharger without interruption.
However, in contemporary engines with the aforementioned electronic engine control, this has undesired effects on the sensor technology in the engine control.
Therefore, the object of the invention is to provide a way in which to retrofit a supercharger designed for uninterrupted operation with an electromagnetic clutch, or control the clutch.
This object is achieved according to the invention by securing a sleeve non-rotationally to the input shaft, pivoting the pulley to the sleeve, and flanging the multi-plate carrier to the front of the sleeve.
The invention is based on the general idea of using the input shaft of the superchargers for mounting the multi-plate carrier non-rotationally relative to the input shaft, and for mounting the pulley rotationally relative to the input shaft, and hence for holding the input and output of the electromagnetic clutch. This eliminates the need for stationary bearing parts for the pulley. At the same time, the multi-plate carrier and pulley can be centered relative to each other without any noteworthy structural outlay.
In a preferred embodiment of the invention, a flange plate that carries the fixed ring magnet or ring coil device and has an opening penetrated by the input shaft and situated inside the ring magnet or ring coil device is secured to a flange surface on the supercharger casing from which the input shaft projects.
In this way, the ring magnet or ring coil device can be fixed in place, eliminating the need for sliding contacts or the like for power supply.
The connecting cables of the ring magnet or ring coil device are preferably accommodated and protected in a recess formed in the flange plate, in particular a groove, which can be arranged on the side of the flange plate facing the supercharger casing in a particularly expedient embodiment of the invention, so that the aforementioned cables are accommodated in a channel enveloped by the supercharger and flange plate after assembly of the flange plate.
The switchable clutch is actuated according to the invention from a control system, which only permits closing of the clutch at above a combustion engine speed threshold, or above a parameter correlated with the aforementioned speed, and allows the clutch to first run through a prescribed slip phase on closing.
In this case, the general idea of providing a switchable clutch with controllable clutch moment, i.e., with controllable transferable moment, between the supercharger and combustion engine is realized. This places only a moderate load on the combustion engine and supercharger as well as the drive connection between the engine and supercharger on closing of the clutch. In particular undesired load peaks are avoided, so that the drive connection can exhibit a comparatively simple structure, and neither the bearings for the moveable compressor elements of the supercharger nor the bearings of the supercharger-driving engine elements, e.g., camshaft, need not be reinforced.
In a particularly preferred embodiment of the invention, al electromagnetic clutch is provided, wherein the controller changes an electrical clutch current with delays or in multiple stages while engaging the clutch.
This ensures a good controllability for the clutch.
With respect to preferred features of the invention, reference is otherwise made to the claims and following explanation of the drawing, based upon which an especially preferred embodiment of the invention is described.